In the land of Reveur there exists a legend of the Silver Siren, a monstrous being who with words alone can topple entire civilizations. People have long learned the legend, to fear those with silver hair, and to flee from those who dare mutter the words of Song!

Meet Kanon, a shy everyday high school student preparing for her graduation with a final tour of her school. Singing a mysterious sheet music she found in the school music room sends her to a fantastic alternate world of adventure, cursed Sorcerers, war-torn lands, monsters, and skilled mercenaries. But she soon learns that in this strange new world of magic and swordplay, she is perhaps the greatest threat of all. Will Kanon survive in this fantasy world where people view her as a nightmare made reality? Let the Song begin, for nothing else will save her…!

(Source: Cross Infinite World)